Nitrogen Doped Carbon Dots for Live Cell Imaging and Tissue Dependent Affinity for Live Zebrafish Imaging

Vijay Bhooshan Kumar vijay.kumar@biu.ac.il ¹ Aharon Gedanken ¹ Zeev Porat ² Deepak Kumar Khajuria ³ Yoni Sheinberger ⁴ Yaron Shav-Tal ⁴ David Karasik ³

¹Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
²Division of Chemistry, Nuclear Research Center-Negev, Negev, Israel
³The Musculoskeletal Genetics Laboratory, Faculty of Medicine in the Galilee, Bar-Ilan University, Safed, Israel
⁴Mina and Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan, Israel

Carbon-based nanodots (CDs) are widely investigated due to their low toxicity, outstanding water solubility and biocompatibility. Specifically, fluorescent CDs have attracted ever-increasing interest. However, so far, only a few studies have focused on assessing the fluorescence of nitrogen-doped CDs (N@CDs) during in-vivo exposure. Here, we describe a strategy for low cost, one-pot synthesis of N@CDs by hydrothermally reacting an aqueous solution of Bovine Serum Albumin (BSA). The as-prepared N@C-dots exhibited high quantum yield (44 %), high photostability, colloidal stability, and high functionalization efficiency. In addition to their low cost, the N@C-dots have demonstrated a non-toxic and long-lasting effect when applied for imaging human cells (human osteosarcoma (U2OS) cells). Further, N@CDs for fluorescence imaging are validated using zebrafish (ZF) as a model. Strong fluorescence emission from ZF embryos and larvae successfully confirms the distribution of N@CDs in ZF. The retention of N@C-dots is very stable, long lasting and with no detectable toxicity. The presence of strong fluorescence at the yolk sac, especially in vicinity to the intestine, suggests that a high content of N@CDs entered the digestive system. This indicates that, N@CDs may have potential imaging applications in elucidating different aspects of lipoprotein and nutritional biology, in a ZF yolk lipid transport and metabolism model. On the other hand, the presence of strong selective florescence at the eyes and melanophore strips at the trunk and tail region of ZF larvae suggests that N@CDs has strong melanin binding affinity. These observations support a novel and revolutionary use of N@CDs as highly specific bioagents for eye and skin imaging and diagnosis. N@CDs are known for their multifunctional applications as highly specific bioagents for various biomedical applications, because of their exceptional biocompatibility, photostability and selective affinity. These characteristics were validated in the developmental ZF model.